CA 19-9
Definition
Measures a protein in the blood called CA 19-9 (cancer antigen 19-9). It is a tumor marker, a substance produced by cancer cells or by normal cells responding to cancer. It is used mainly for monitoring pancreatic cancer.
Purpose
To monitor the course of the cancer and the effectiveness of treatment (the level rises as the tumor grows and falls as it shrinks); to help determine prognosis and stage; to detect recurrence after treatment.
Results
| Change | Interpretation |
|---|---|
| Rising | The tumor may be growing; treatment may not be working |
| Falling | The tumor may be shrinking; treatment appears to be working |
| Stable | The disease is unchanged |
| Rising after treatment | Possible recurrence |
Normal Values
Laboratory specific.
Risks and Limitations
This marker has a very important limitation of its own:
Some people do not produce CA 19-9 even when they have a cancer that usually produces high levels.
(These are Lewis antigen negative individuals.) In other words, a normal CA 19-9 does not rule out pancreatic cancer.
Other limitations:
- Not suitable for screening on its own
- Non-cancer causes of elevation: gallstones, pancreatitis, liver disease, cystic fibrosis
- It can also be high in healthy people